1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
|
<?xml version="1.0" encoding="utf-8" ?>
<!--
-
- This file is part of the OpenLink Software Virtuoso Open-Source (VOS)
- project.
-
- Copyright (C) 1998-2018 OpenLink Software
-
- This project is free software; you can redistribute it and/or modify it
- under the terms of the GNU General Public License as published by the
- Free Software Foundation; only version 2 of the License, dated June 1991.
-
- This program is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- General Public License for more details.
-
- You should have received a copy of the GNU General Public License along
- with this program; if not, write to the Free Software Foundation, Inc.,
- 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
-
-
-->
<sect1 id="xmltype"><title>XMLType</title>
<para>
XMLType is a predefined type for representing XML entities as UDT objects.
This is compatible with Oracle9i and later.
You can get better performance and flexibility by using use plain built-in functions
that directly operate with XML entities.
All predefined member functions of XMLType for extracting fragments from
an XMLType are actually wrappers for <link linkend="fn_xpath_eval"><function>xpath_eval()</function></link> built-in function.
You can declare a column of XMLType but the actual type of the created column will be "LONG XML".
Thus any XML-related feature that can be used for "LONG XML" column will work with XMLType.
E.g. <link linkend="sqlrefcreattablewithschema">WITH SCHEMA constraint</link> allows you to force stored values
to match a particular schema; <link linkend="usingxmlfreetext">XML free text index</link> can accelerate search for documents by content
etc.
</para>
<para>
XMLType behaves like any user-defined type, with the only difference in type conversion rules.
If an XML entity is passed as an argument instead of an instance of XMLType, a new instance of
XMLType is created by a constructor that takes the entity as an argument.
Similarly, functions that accept XML entities as arguments can also accept an instance of
XMLType as an actual value of argument.
</para>
<para>
The following example creates a table with an XMLType column, put two records there
and performs a simple search:</para>
<screen><![CDATA[
CREATE TABLE Xml_tab ( xmlval XMLType);
INSERT INTO Xml_tab VALUES (
xmltype('<?xml version="1.0"?>
<EMP>
<EMPNO>221</EMPNO>
<ENAME>John</ENAME>
</EMP>'));
INSERT INTO Xml_tab VALUES (
xmltype('<?xml version="1.0"?>
<PO>
<PONO>331</PONO>
<PONAME>PO_1</PONAME>
</PO>'));
-- now extract the numerical values for the employee numbers
SELECT e.xmlval.extract('//EMPNO/text()').getNumVal() as empno
FROM Xml_tab
WHERE e.xmlval.existsnode('/EMP/EMPNO') = 1;
]]></screen>
<para>To create a new instance of XMLType, the constructor <link linkend="fn_XMLType.XMLType"><function>XMLType()</function></link>
or a function <link linkend="fn_createXML"><function>createXML()</function></link> is used.
</para>
<para>
Virtuoso can perform XPATH search in XMLType instances:
<link linkend="fn_XMLType.extract"><function>extract()</function></link>
and
<link linkend="fn_XMLType.existsNode"><function>existsNode()</function></link>
member functions are convenient for simple searches and any
built-in XPATH functions like
<link linkend="fn_xpath_eval"><function>xpath_eval()</function></link> or
<link linkend="fn_xquery_eval"><function>xquery_eval()</function></link> can handle
XMLType parameters instead of XML entity parameters.
An application can use
<link linkend="fn_XMLType.getStringVal"><function>getStringVal()</function></link>,
<link linkend="fn_XMLType.getNumVal"><function>getNumVal()</function></link> and
<link linkend="fn_XMLType.getClobVal"><function>getColbVal()</function></link>
member functions to convert found node to strings, numbers or an XML source text of the node.
</para>
<para>Instances of the type can store the URL of the XML schema to which they should conform.
This URL can be specified when an instance is constructed;
Once an instance is created, its schema URL cannot be changed but a modified copy can be created by
<link linkend="fn_XMLType.createSchemaBasedXML"><function>createSchemaBasedXML()</function></link>
and
<link linkend="fn_XMLType.createNonSchemaBasedXML"><function>createNonSchemaBasedXML()</function></link>
member functions;
<link linkend="fn_XMLType.isSchemaBased"><function>isSchemaBased()</function></link>
and <link linkend="fn_XMLType.getSchemaURL"><function>getSchemaURL()</function></link>
member functions check whether the given instance is schema based or not and
what particular schema is used.
</para>
<para>
An schema based XMLType instance can be validated against its schema;
If it has been validated against its schema once with no errors detected then
a special "VALIDATED" flag is set
in the instance indicating that there is no need to validate it again.
<link linkend="fn_XMLType.schemaValidate"><function>schemaValidate()</function></link>
member function performs the validation,
<link linkend="fn_XMLType.isSchemaValidated"><function>isSchemaValidated()</function></link>
queries the "VALIDATED" flag and
<link linkend="fn_XMLType.setSchemaValidated"><function>setSchemaValidated()</function></link>
changes the "VALIDATED" flag if application needs optimization tricks.
</para>
<para>
In addition, any instance can be validated against an arbitrary schema via member function
<link linkend="fn_XMLType.isSchemaValid"><function>isSchemaValid()</function></link>.
Built-in function <link linkend="xml_validate_schema"><function>xml_validate_schema()</function></link>
may accept instance of XMLType as its first argument, providing even more
validation functionality.
</para>
</sect1>
|
